/*
 * Copyright 2014-2015 Open Networking Laboratory
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.onlab.util;

import static java.nio.file.Files.delete;
import static java.nio.file.Files.walkFileTree;
import static org.onlab.util.GroupedThreadFactory.groupedThreadFactory;
import static org.slf4j.LoggerFactory.getLogger;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.nio.ByteBuffer;
import java.nio.charset.StandardCharsets;
import java.nio.file.FileVisitResult;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.nio.file.SimpleFileVisitor;
import java.nio.file.StandardCopyOption;
import java.nio.file.attribute.BasicFileAttributes;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Dictionary;
import java.util.List;
import java.util.Random;
import java.util.concurrent.CompletableFuture;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.Future;
import java.util.concurrent.ThreadFactory;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;
import java.util.function.Function;
import java.util.function.Supplier;
import java.util.stream.Stream;
import java.util.stream.StreamSupport;

import org.slf4j.Logger;

import com.google.common.base.Strings;
import com.google.common.primitives.UnsignedLongs;
import com.google.common.util.concurrent.ThreadFactoryBuilder;

/**
 * Miscellaneous utility methods.
 */
public abstract class Tools {

    private Tools() {
    }

    private static final Logger log = getLogger(Tools.class);

    private static Random random = new Random();

    /**
     * Returns a thread factory that produces threads named according to the
     * supplied name pattern.
     *
     * @param pattern name pattern
     * @return thread factory
     */
    public static ThreadFactory namedThreads(String pattern) {
        return new ThreadFactoryBuilder()
                .setNameFormat(pattern)
                .setUncaughtExceptionHandler((t, e) -> log.error("Uncaught exception on " + t.getName(), e))
                .build();
    }

    /**
     * Returns a thread factory that produces threads named according to the
     * supplied name pattern and from the specified thread-group. The thread
     * group name is expected to be specified in slash-delimited format, e.g.
     * {@code onos/intent}. The thread names will be produced by converting
     * the thread group name into dash-delimited format and pre-pended to the
     * specified pattern.
     *
     * @param groupName group name in slash-delimited format to indicate hierarchy
     * @param pattern   name pattern
     * @return thread factory
     */
    public static ThreadFactory groupedThreads(String groupName, String pattern) {
        return new ThreadFactoryBuilder()
                .setThreadFactory(groupedThreadFactory(groupName))
                .setNameFormat(groupName.replace(GroupedThreadFactory.DELIMITER, "-") + "-" + pattern)
                .setUncaughtExceptionHandler((t, e) -> log.error("Uncaught exception on " + t.getName(), e))
                .build();
    }

    /**
     * Returns a thread factory that produces threads with MIN_PRIORITY.
     *
     * @param factory backing ThreadFactory
     * @return thread factory
     */
    public static ThreadFactory minPriority(ThreadFactory factory) {
        return new ThreadFactoryBuilder()
                .setThreadFactory(factory)
                .setPriority(Thread.MIN_PRIORITY)
                .build();
    }

    /**
     * Returns true if the collection is null or is empty.
     *
     * @param collection collection to test
     * @return true if null or empty; false otherwise
     */
    public static boolean isNullOrEmpty(Collection collection) {
        return collection == null || collection.isEmpty();
    }

    /**
     * Returns the specified item if that item is not null; otherwise throws
     * not found exception.
     *
     * @param item    item to check
     * @param message not found message
     * @param <T>     item type
     * @return item if not null
     * @throws org.onlab.util.ItemNotFoundException if item is null
     */
    public static <T> T nullIsNotFound(T item, String message) {
        if (item == null) {
            throw new ItemNotFoundException(message);
        }
        return item;
    }

    /**
     * Returns the specified item if that item is not null; otherwise throws
     * bad argument exception.
     *
     * @param item    item to check
     * @param message not found message
     * @param <T>     item type
     * @return item if not null
     * @throws IllegalArgumentException if item is null
     */
    public static <T> T nullIsIllegal(T item, String message) {
        if (item == null) {
            throw new IllegalArgumentException(message);
        }
        return item;
    }

    /**
     * Converts a string from hex to long.
     *
     * @param string hex number in string form; sans 0x
     * @return long value
     */
    public static long fromHex(String string) {
        return UnsignedLongs.parseUnsignedLong(string, 16);
    }

    /**
     * Converts a long value to hex string; 16 wide and sans 0x.
     *
     * @param value long value
     * @return hex string
     */
    public static String toHex(long value) {
        return Strings.padStart(UnsignedLongs.toString(value, 16), 16, '0');
    }

    /**
     * Converts a long value to hex string; 16 wide and sans 0x.
     *
     * @param value long value
     * @param width string width; zero padded
     * @return hex string
     */
    public static String toHex(long value, int width) {
        return Strings.padStart(UnsignedLongs.toString(value, 16), width, '0');
    }

    /**
     * Returns a copy of the input byte array.
     *
     * @param original input
     * @return copy of original
     */
    public static byte[] copyOf(byte[] original) {
        return Arrays.copyOf(original, original.length);
    }

    /**
     * Get property as a string value.
     *
     * @param properties   properties to be looked up
     * @param propertyName the name of the property to look up
     * @return value when the propertyName is defined or return null
     */
    public static String get(Dictionary<?, ?> properties, String propertyName) {
        Object v = properties.get(propertyName);
        String s = (v instanceof String) ? (String) v :
                v != null ? v.toString() : null;
        return Strings.isNullOrEmpty(s) ? null : s.trim();
    }

    /**
     * Suspends the current thread for a specified number of millis.
     *
     * @param ms number of millis
     */
    public static void delay(int ms) {
        try {
            Thread.sleep(ms);
        } catch (InterruptedException e) {
            throw new RuntimeException("Interrupted", e);
        }
    }

    /**
     * Returns a function that retries execution on failure.
     * @param base base function
     * @param exceptionClass type of exception for which to retry
     * @param maxRetries max number of retries before giving up
     * @param maxDelayBetweenRetries max delay between successive retries. The actual delay is randomly picked from
     * the interval (0, maxDelayBetweenRetries]
     * @return function
     * @param <U> type of function input
     * @param <V> type of function output
     */
    public static <U, V> Function<U, V> retryable(Function<U, V> base,
            Class<? extends Throwable> exceptionClass,
            int maxRetries,
            int maxDelayBetweenRetries) {
        return new RetryingFunction<>(base, exceptionClass, maxRetries, maxDelayBetweenRetries);
    }

    /**
     * Returns a Supplier that retries execution on failure.
     * @param base base supplier
     * @param exceptionClass type of exception for which to retry
     * @param maxRetries max number of retries before giving up
     * @param maxDelayBetweenRetries max delay between successive retries. The actual delay is randomly picked from
     * the interval (0, maxDelayBetweenRetries]
     * @return supplier
     * @param <V> type of supplied result
     */
    public static <V> Supplier<V> retryable(Supplier<V> base,
            Class<? extends Throwable> exceptionClass,
            int maxRetries,
            int maxDelayBetweenRetries) {
        return () -> new RetryingFunction<>(v -> base.get(),
                exceptionClass,
                maxRetries,
                maxDelayBetweenRetries).apply(null);
    }

    /**
     * Suspends the current thread for a random number of millis between 0 and
     * the indicated limit.
     *
     * @param ms max number of millis
     */
    public static void randomDelay(int ms) {
        try {
            Thread.sleep(random.nextInt(ms));
        } catch (InterruptedException e) {
            throw new RuntimeException("Interrupted", e);
        }
    }

    /**
     * Suspends the current thread for a specified number of millis and nanos.
     *
     * @param ms    number of millis
     * @param nanos number of nanos
     */
    public static void delay(int ms, int nanos) {
        try {
            Thread.sleep(ms, nanos);
        } catch (InterruptedException e) {
            throw new RuntimeException("Interrupted", e);
        }
    }

    /**
     * Slurps the contents of a file into a list of strings, one per line.
     *
     * @param path file path
     * @return file contents
     * @deprecated in Emu release
     */
    @Deprecated
    public static List<String> slurp(File path) {
        try (
            BufferedReader br = new BufferedReader(
                    new InputStreamReader(new FileInputStream(path), StandardCharsets.UTF_8));
                ) {
            List<String> lines = new ArrayList<>();
            String line;
            while ((line = br.readLine()) != null) {
                lines.add(line);
            }
            return lines;

        } catch (IOException e) {
            return null;
        }
    }

    /**
     * Purges the specified directory path.&nbsp;Use with great caution since
     * no attempt is made to check for symbolic links, which could result in
     * deletion of unintended files.
     *
     * @param path directory to be removed
     * @throws java.io.IOException if unable to remove contents
     */
    public static void removeDirectory(String path) throws IOException {
        DirectoryDeleter visitor = new DirectoryDeleter();
        File dir = new File(path);
        if (dir.exists() && dir.isDirectory()) {
            walkFileTree(Paths.get(path), visitor);
            if (visitor.exception != null) {
                throw visitor.exception;
            }
        }
    }

    /**
     * Purges the specified directory path.&nbsp;Use with great caution since
     * no attempt is made to check for symbolic links, which could result in
     * deletion of unintended files.
     *
     * @param dir directory to be removed
     * @throws java.io.IOException if unable to remove contents
     */
    public static void removeDirectory(File dir) throws IOException {
        DirectoryDeleter visitor = new DirectoryDeleter();
        if (dir.exists() && dir.isDirectory()) {
            walkFileTree(Paths.get(dir.getAbsolutePath()), visitor);
            if (visitor.exception != null) {
                throw visitor.exception;
            }
        }
    }

    // Auxiliary path visitor for recursive directory structure removal.
    private static class DirectoryDeleter extends SimpleFileVisitor<Path> {

        private IOException exception;

        @Override
        public FileVisitResult visitFile(Path file, BasicFileAttributes attributes)
                throws IOException {
            if (attributes.isRegularFile()) {
                delete(file);
            }
            return FileVisitResult.CONTINUE;
        }

        @Override
        public FileVisitResult postVisitDirectory(Path directory, IOException ioe)
                throws IOException {
            delete(directory);
            return FileVisitResult.CONTINUE;
        }

        @Override
        public FileVisitResult visitFileFailed(Path file, IOException ioe)
                throws IOException {
            this.exception = ioe;
            return FileVisitResult.TERMINATE;
        }
    }

    /**
     * Returns a human friendly time ago string for a specified system time.
     *
     * @param unixTime system time in millis
     * @return human friendly time ago
     */
    public static String timeAgo(long unixTime) {
        long deltaMillis = System.currentTimeMillis() - unixTime;
        long secondsSince = (long) (deltaMillis / 1000.0);
        long minsSince = (long) (deltaMillis / (1000.0 * 60));
        long hoursSince = (long) (deltaMillis / (1000.0 * 60 * 60));
        long daysSince = (long) (deltaMillis / (1000.0 * 60 * 60 * 24));
        if (daysSince > 0) {
            return String.format("%dd ago", daysSince);
        } else if (hoursSince > 0) {
            return String.format("%dh ago", hoursSince);
        } else if (minsSince > 0) {
            return String.format("%dm ago", minsSince);
        } else if (secondsSince > 0) {
            return String.format("%ds ago", secondsSince);
        } else {
            return "just now";
        }
    }

    /**
     * Copies the specified directory path.&nbsp;Use with great caution since
     * no attempt is made to check for symbolic links, which could result in
     * copy of unintended files.
     *
     * @param src directory to be copied
     * @param dst destination directory to be removed
     * @throws java.io.IOException if unable to remove contents
     */
    public static void copyDirectory(String src, String dst) throws IOException {
        walkFileTree(Paths.get(src), new DirectoryCopier(src, dst));
    }

    /**
     * Copies the specified directory path.&nbsp;Use with great caution since
     * no attempt is made to check for symbolic links, which could result in
     * copy of unintended files.
     *
     * @param src directory to be copied
     * @param dst destination directory to be removed
     * @throws java.io.IOException if unable to remove contents
     */
    public static void copyDirectory(File src, File dst) throws IOException {
        walkFileTree(Paths.get(src.getAbsolutePath()),
                     new DirectoryCopier(src.getAbsolutePath(),
                                         dst.getAbsolutePath()));
    }

    /**
     * Returns the future value when complete or if future
     * completes exceptionally returns the defaultValue.
     *
     * @param future future
     * @param defaultValue default value
     * @param <T> future value type
     * @return future value when complete or if future
     * completes exceptionally returns the defaultValue.
     */
    public static <T> T futureGetOrElse(Future<T> future, T defaultValue) {
        try {
            return future.get();
        } catch (InterruptedException e) {
            Thread.currentThread().interrupt();
            return defaultValue;
        } catch (ExecutionException e) {
            return defaultValue;
        }
    }

    /**
     * Returns the future value when complete or if future
     * completes exceptionally returns the defaultValue.
     *
     * @param future future
     * @param timeout time to wait for successful completion
     * @param timeUnit time unit
     * @param defaultValue default value
     * @param <T> future value type
     * @return future value when complete or if future
     * completes exceptionally returns the defaultValue.
     */
    public static <T> T futureGetOrElse(Future<T> future,
                                        long timeout,
                                        TimeUnit timeUnit,
                                        T defaultValue) {
        try {
            return future.get(timeout, timeUnit);
        } catch (InterruptedException e) {
            Thread.currentThread().interrupt();
            return defaultValue;
        } catch (ExecutionException | TimeoutException e) {
            return defaultValue;
        }
    }

    /**
     * Returns a future that is completed exceptionally.
     *
     * @param t exception
     * @param <T> future value type
     * @return future
     */
    public static <T> CompletableFuture<T> exceptionalFuture(Throwable t) {
        CompletableFuture<T> future = new CompletableFuture<>();
        future.completeExceptionally(t);
        return future;
    }

    /**
     * Returns the contents of {@code ByteBuffer} as byte array.
     * <p>
     * WARNING: There is a performance cost due to array copy
     * when using this method.
     *
     * @param buffer byte buffer
     * @return byte array containing the byte buffer contents
     */
    public static byte[] byteBuffertoArray(ByteBuffer buffer) {
        int length = buffer.remaining();
        if (buffer.hasArray()) {
            int offset = buffer.arrayOffset() + buffer.position();
            return Arrays.copyOfRange(buffer.array(), offset, offset + length);
        }
        byte[] bytes = new byte[length];
        buffer.duplicate().get(bytes);
        return bytes;
    }

    /**
     * Converts an iterable to a stream.
     *
     * @param it iterable to convert
     * @param <T> type if item
     * @return iterable as a stream
     */
    public static <T> Stream<T> stream(Iterable<T> it) {
        return StreamSupport.stream(it.spliterator(), false);
    }

    // Auxiliary path visitor for recursive directory structure copying.
    private static class DirectoryCopier extends SimpleFileVisitor<Path> {
        private Path src;
        private Path dst;
        private StandardCopyOption copyOption = StandardCopyOption.REPLACE_EXISTING;

        DirectoryCopier(String src, String dst) {
            this.src = Paths.get(src);
            this.dst = Paths.get(dst);
        }

        @Override
        public FileVisitResult preVisitDirectory(Path dir, BasicFileAttributes attrs) throws IOException {
            Path targetPath = dst.resolve(src.relativize(dir));
            if (!Files.exists(targetPath)) {
                Files.createDirectory(targetPath);
            }
            return FileVisitResult.CONTINUE;
        }

        @Override
        public FileVisitResult visitFile(Path file, BasicFileAttributes attrs) throws IOException {
            Files.copy(file, dst.resolve(src.relativize(file)), copyOption);
            return FileVisitResult.CONTINUE;
        }
    }

}